1. Field of the Invention
The present invention relates to a head support mechanism provided by assembling a support arm and a suspension, a head arm assembly (HAA) provided by mounting a flying type head slider for supporting a recording and/or reproducing head element such as a thin-film magnetic head or an optical head on the head support mechanism, and a disk drive apparatus provided with the HAA.
2. Description of the Related Art
In a magnetic disk drive apparatus, at least one magnetic head slider attached to a leading end section of an HAA is flying on a surface of a rotating magnetic disk. In this state, a thin-film magnetic head element formed on the magnetic head slider records and/or reproduces data on/or from the magnetic disk.
The HAA mainly has a magnetic head slider, a suspension with an elastic flexure that supports the magnetic head slider, an elastic load beam that supports the flexure at its leading end section and a base plate that supports a trailing end section of the load beam, and a rigid support arm that supports the suspension. A load to be applied on the magnetic head slider toward the surface of the magnetic disk is generated in a plate spring section provided in the middle of the load beam of the suspension.
Such a conventional HAA has a cantilever structure for supporting the suspension at its trailing end section. The cantilever structure is excellent in stabilizing the load applied on the magnetic head slider and saving a required space. However, the cantilever structure has a serious problem of a low shock resistance. Specifically, because the magnetic head slider is mounted at a leading end section of the HAA which is a free end of the cantilever structure, when a shock force is applied, the rotation moment of the magnetic head slider is added to a rotation moment based upon the mass of the whole system of the beam structure. As a result, a slap mode occurs in which the head slider jumps up from the magnetic disk surface or is slapped against the surface. According to the conventional HAA, this tendency is significantly observed, because the load beam, which is a beam structure supporting the magnetic head slider, is formed by a spring member of a low rigidity, namely a stainless steel plate slightly thicker than the flexure.
In a magnetic disk drive for 3.5-inch disks, which is mounted in a computer called a high-end type or desktop type, an excessive shock force is rarely applied. However, in a magnetic disk drive for 2.5-inch disks, which is mounted in a notebook computer, an excessive shock force is likely to be applied. Accordingly, the low shock resistance is a serious problem.
U.S. Pat. No. 6,751,064 B2 proposes a head support apparatus in which to improve the shock resistance of an HAA, a rigid arm is provided with a magnetic head slider at one end and voice coil motor (VCM) for horizontal rotation at the other end. Further, in this apparatus, the arm is configured to rotatively move in a radial direction of the magnetic disk around a bearing section and is also configured to have a balance structure in which the arm can be rotatively moved in a direction perpendicular to the magnetic disk surface around a bearing section. Moreover, a pivot is used to urge a plate spring plate provided in the bearing section to apply a load to the magnetic head slider.
In such HAA with the balance structure, because the distance between the VCM and the magnetic head slider is short in case of a small-diameter magnetic disk apparatus such as a micro drive and a single disk, the weight of a part of the arm in the VCM side from the bearing section can be balanced with a part of the arm in the magnetic head slider side from the bearing section. However, in a larger-diameter magnetic disk drive for, for example, 1.8-inch or 2.5-inch disks, the arm is longer, so that it is difficult to ensure a sufficient shock resistance. Moreover, since the VCM is used to balance the balance structure, the magnetic disk apparatus cannot be configured so as to allow a plurality of HAAs with the balance structure to stack each other.
To eliminate such an inconvenience, inventors of the present application proposed the employment of a balance structure at a leading end section of a support arm.
FIG. 1 is a side view illustrating a schematic configuration of an HAA proposed by the inventors.
In the figure, reference numeral 10 designates a support arm. Reference numeral 11 designates a load beam of a balance structure that uses as a fulcrum a load support point 12, that is, a projection provided at a leading end section of the support arm 10. Reference numeral 13 designates a support spring for coupling the load beam 11 and the support arm 10 together to urge the load beam 11 via the projection 12. Reference numeral 14 designates a magnetic head slider supported at a leading end section of the load beam 11 via the flexure 15. Reference numeral 16 designates a magnetic disk.
In this HAA, since the load beam 11 of the balance structure is provided at the leading end section of the support arm 10, the increased length of the support arm does not substantially reduce the shock resistance. Also, because this structure does not use a coil section of a VCM to balance the balance structure, the magnetic disk apparatus can be configured so as to allow a plurality of HAAs to stack each other.
However, according to the HAA of the structure shown in FIG. 1, since a trailing end section (lying opposite the end at which the magnetic head slider 14 is mounted) 11a of the load beam 11 is extended to balance rotation moments, when the HAA receives a shock, the extended part is displaced. That is, in order to make the rotation moment of the part between the projection or load support point 12 and the leading end section (magnetic head slider side) equal to the rotation moment of the part between the projection or load support point 12 and the trailing end section (actuator (VCM) side), it is necessary to extend the trailing end section 11a of the load beam 11 or to attach a weight close to the trailing end section 11a. In this case, when a shock is applied, the trailing end section is displaced to interfere with the support arm 10 or the magnetic disk 16. Even when no shock is applied, if the magnetic disk apparatus employs a load unload system, the trailing end section 11a of the load beam 11 may contact with the surface of the magnetic disk 16. Thus, any increase in the magnitude of displacement in this trailing end section is undesirable.
Also, since the support arm is long, it is necessary to greatly increase its thickness to prevent the arm itself from being deformed by a shock. Furthermore, because the extended trailing end section 11a of the load beam 11 or the weight attached to the trailing end section is at a substantial distance from the horizontal axis of rotation (the center of seek rotation), disadvantageously, an inertia moment during a seek operation may directly increase. In addition, since the weight is provided in a gap between the support arm and the magnetic disk, it is difficult to optimize the shape of the weight. Namely, it is quite difficult to make a weight shape suitable for bending characteristics or torsion and sway characteristics.